In 1998, Midrex International received U.S. Pat. No. 5,730,775, that teaches an improved method (known by the service mark of FASTMET7) and apparatus for producing direct reduced iron from dry iron oxide and carbon compacts that are placed onto a rotary hearth, and are metallized by heating the compacts for a short time period. For a general understanding of the recent art, U.S. Pat. No. 5,730,775 is herein incorporated by reference.
Improvements in efficiency have been attempted within the industry with furnace modifications that provide a vitreous hearth layer that remains vitrified at increased temperatures, with a modification that provides an additional hearth coating to allow for shortened processing time of iron oxide compacts. Coating of the hearth surface facilitates product removal, reduces loss of purified molten iron onto the vitreous hearth layer and/or reduces loss on the interior surfaces of furnaces from the protective coating of surfaces with metallized iron oxides during processing and reducing operations. The above described hearth coatings add additional costs by adding materials onto the hearth layers, add to the complexity of reactions occurring within the furnace, and add additional processing time for the hearth coatings to cure onto the hearth surfaces.
Improvements are sought within the metal production industry for treatment with coatings of carbonaceous feed material before placement within a furnace, the coatings providing improved metallization of compounds within the furnace without additional treatment and coatings on the furnace hearth surface, or in conjunction with limited hearth surface conditioning.